2011/11/18 Patrik Thunström <patrik.thunstrom_at_bassetglobal.com>:
>
> I just sent over a report of our findings to the libcURL dev mailing list,
> mainly telling that when using libcURL with various internal buffer sizes,
> download and upload performance is going in in opposite directions, upload
> is only improved by a larger buffer, whereas download is severely decreased.
...
>
> This using libcURL 7.22.0, libssh 1.3.0 and OpenSSL 1.0.0e, on a Win32
> platform (customer was running Windows Server 2003, but our local testing
> was with Windows 7)
...
> One thing that can be noticed is that it does not seem to be the actual
> transfer that is taking time; libcURL’s progress callback returns with info
> that it has downloaded the full amount of data a lot earlier than returning
> control to the program.

This behaviour is sounds like a problem with 1.3.0 that was
(partially) fixed recently. Have you tried the latest from git?